Beer Blending and IBUs

I'm going to do do a new beer in a few days, and for various reasons I'm planning on fermenting two small batches separately and then combining them together.

My only real concern is how the ABV and IBUs will be impacted doing it this way (if at all), compared to brewing all the ingredients together and fermenting it as one regular sized batch. I spec'd out the ABV and IBUs (assuming the efficiency is the same for all three batches) of the two batches separately and together:

Beer One:
5% ABV
43 IBU

Beer Two:
7.5% ABV
53 IBU

Blended:
?? ABV
?? IBU

Brewed and fermented together:
6.5% ABV
61 IBU


I would think that combining the two beers after fermentation would yield results similar to if all the ingredients were brewed and fermented together, simply because I can't see why it wouldn't do that. But I was wondering if anyone else had any experience in this, and had any ideas of what might happen?

In theory, it wouldn't matter. In practice it may, due to things like different yeast pitching and different fermentation temperatures.

Are you going to add equal volumes of both together? In any case the equation is going to be the same.

[(x proportion of total blended volume) * (ABV or IBUs) for beer 1] + [(x proportion of total blended volume) * (ABV or IBUs) for beer 2].

If you used equal volumes, your x would be .5 for both. If you used 3 gallons of beer 1 and 2 gallons of beer 2, your x's would be .6 and .4 respectively.

ah that makes sense. I undid some mistakes I had in my combined recipe and the formula you gave me matched the the recipe. thanks!